Ionic Currents as Control Mechanism in Cytomorphogenesis

Abstract

As plant cells develop into multicellular organisms, three-dimensional patterns are formed without the cells possessing genetically laid down plans for these patterns. Therefore, a cell needs additional information for its proper spatial development to indicate, for instance, in which direction it should grow or in which plane it should divide. This information generally comes from external physical factors such as light, gravity, or pressure or from chemical factors such as ion or hormone gradients. Some examples of the effects of such factors on the morphogenesis of plant cells are illustrated in Figs. 1 and 2. When, for instance, zygotes of the brown algae Fucus and Pelvetia, which are practically nonpolar cells, are exposed to light from one side or only partly illuminated or exposed to a K⁺ gradientthey grow on the side turned away from the light or at the shaded side or on the side with the higher K⁺ concentration, respectively (Bentrup 1971, Bentrup et al. 1967, Jaffe 1968). When the tip-growing tubes of the yellow-green alga Vaucheria are locally irradiated with blue light, an additional growth zone is formed on this spot, which leads to branching within a few hours (Kicherer and Weisenseel, unpublished).